Salk finds key step for healthy brains

The Salk Institute of Biological Studies in La Jolla has discovered a subtle bit of chemistry that appears to be essential for the normal development of the brain in humans and mice.

The discovery involves cytosine, one of the four main units of DNA. Scientists found that the chemical make-up of cytosine is modified in some neurons, helping the brain grow in a healthy way from the fetal stage through adulthood. Scientists knew that this kind of change could happen in stem cells before the cells begin to turn into specific types of tissue. But it wasn’t known that it happens beyond that point.

The insight represents a potentially important finding in epigenetics, the rapidly emerging study of factors that affect the behavior of genes.

“This chemical modification is silencing genes, leaving behind marks that we were able to map out,” said Salk biologist Joseph Ecker, lead author of the study that identifies the process. “This gives us a look at how a healthy brain develops. Now, we’ll compare the process to brains where mental disorders have developed.”

The advance was published July 4th in the journal Science.

The study focused on the frontal cortex, the region of brain associated with problem solving and language. This region also is involved in many mental disabilities. Both are increasingly drawing the attention of experts in epigenetics.

Ryan Lister, a Salk postdoctoral fellow who co-author the Science paper, said in a statement, “We are only now coming to understand the role epigenetics plays in disease and in how humans and other organisms develop and adapt to their environment. If you only look at genes, you find that there is a lot of variation between individuals that isn’t accounted for by the genome along. The epigenome may be the source of that variation.”